Bio-mechanical prosthetic finger with y-shaped rocker

ABSTRACT

The disclosure provides apparatus and methods of use pertaining to a prosthetic finger assembly. In one embodiment, the assembly includes a coupling tip and a distal ring coupled with the coupling tip. The assembly further includes a proximal ring coupled with the distal ring. A rocker formed in a Y-shape with a first end forming a single prong and a second end forming a split prong may extend between the coupling tip and the proximal ring. The coupling tip, distal ring, proximal ring, and Y-shaped rocker may all be hingedly connected such that movements of the residual finger within the proximal ring and the distal articulate the distal ring together with the rocker to curl and bend the coupling tip. Other embodiments are also disclosed.

REFERENCE TO PENDING PRIOR PATENT APPLICATION

The application claims the benefit under 35 U.S.C. 119 (e) of U.S.Provisional Patent Application Numbers 62/111,436, filed Feb. 3, 2015 byJon Bengtsson, Robert Thompson, and Charles Colin Macduff for“BIO-MECHANICAL PROSTHETIC FINGER WITH Y-SHAPED ROCKER,” and 62/209,826,filed Aug. 25, 2015 by Robert Thompson JR., Jon Bengtsson, AnthonyCharles Peto, Sydney Tye Minnis, Eric Dennis Klumper, and Bradley ArthurCrittenden for “BIO-MECHANICAL PROSTHETIC FINGER WITH Y-SHAPED ROCKER,”both of which patent applications are hereby incorporated herein byreference.

BACKGROUND

If a person loses a finger, a finger segment, or a fingertip, the resultis impaired performance of the hand. Having an amputated finger inhibitsan amputee from performing some of the most basic tasks. For example,with a lost finger or fingertip, the task of typing on a computerkeyboard or dialing on a telephone becomes significantly more difficult.These types of tasks require precise actions that only fingers are ableto offer.

Not only allowing for the performance of precise physical actions,fingers also provide an increased ability to grip or handle items. Whileholding an item in the hand, the weight of the item is dispersed throughall of a user's fingers. By varying the force used by each finger on theholder's hand, the holder is able to manipulate the item in a myriad ofways. However, if the holder is missing all or even part of a singledigit, or if a digit is present but nonfunctioning, this freedom ofmanipulation and the number of degrees through which the holder canmanipulate the item is drastically decreased.

Current prosthetic finger solutions demonstrate several drawbacks.First, a primary category of prosthetic fingers offers only cosmeticrestoration. These prosthetics are designed to be worn passively andoffer a realistic look. They provide little to no functionality and donot enable the owner to restore functionality to his or her hand. Otherprosthetics offer the user some level of restored functionality, but arecomplex in design and electrically powered. These prosthetics, whileperhaps better than going without, are impractical in that they requirean external power source and can be both bulky and unwieldy for the userto manage. Still other prosthetic fingers are body-powered but lack thedesign flexibility necessary to accommodate any length of residualfinger (e.g., all or partially amputated and varying degrees ofamputation) while providing maximum dexterity, grip strength, and fingerarticulation.

Summary

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key aspects oressential aspects of the claimed subject matter. Moreover, this Summaryis not intended for use as an aid in determining the scope of theclaimed subject matter.

One embodiment provides a biomechanically driven prosthetic fingerassembly. The prosthetic finger assembly includes (1) a coupling tip;(2) a distal ring configured to anchor onto a residual finger, where thedistal ring is rotatively coupled with the coupling tip via a firsthinged connection; (3) a proximal ring configured to anchor onto theresidual finger, where the proximal ring is rotatively coupled with thedistal ring via a second hinged connection, and where the first hingedconnection and the second hinged connection define a midline relative toa z-axis; and (4) a rocker extending between the coupling tip and theproximal ring, the rocker having a first end and a second end inopposition to one another, where the first end rotatively couples withthe coupling tip via a third hinged connection located below themidline, and where the second end rotatively couples with the proximalring via a fourth hinged connection located above the midline. Thedistal ring together with the rocker are configured to utilizearticulation movements of the residual finger within the proximal anddistal rings to emulate a finger's natural closing motion at thecoupling tip.

Another embodiment provides a method of fitting a customized prostheticfinger having a proximal ring configured to anchor to a patient'sresidual finger, the proximal ring containing one or moreshim-retainment apertures. The method begins with inserting the residualfinger into an interior of the proximal ring of the prosthetic fingerand continues with assessing a tightness of the proximal ring about theresidual finger. Next, the method includes selecting a first shim havinga first thickness from a plurality of shims configured to line theinterior of the proximal ring, each of the shims including one or moreretaining grommets, before removing the prosthetic finger from theresidual finger. The method further involves inserting the first shiminto the interior of the proximal ring such that the retaining grommetsprotrude through the shim-retainment apertures, thereby retaining thefirst shim within the interior of the proximal ring, before reinsertingthe residual finger.

Yet another embodiment provides a prosthetic finger device. Theprosthetic finger device includes a rocker having a proximal end and adistal end, where a tip is operably connected with the distal end of therocker. The device also includes a distal linkage operably connectedwith a proximal linkage, where the proximal linkage is in operableconnection with the proximal end of the rocker. The prosthetic fingerdevice further includes a first proximal cage ring coupled with theproximal linkage and a first distal cage ring coupled with the distallinkage.

Other embodiments are also disclosed.

Additional objects, advantages and novel features of the technology willbe set forth in part in the description which follows, and in part willbecome more apparent to those skilled in the art upon examination of thefollowing, or may be learned from practice of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention,including the preferred embodiment, are described with reference to thefollowing figures, wherein like reference numerals refer to like partsthroughout the various views unless otherwise specified. Illustrativeembodiments of the invention are illustrated in the drawings, in which:

FIG. 1 illustrates a perspective view of one embodiment of a prostheticfinger assembly featuring a Y-shaped rocker;

FIG. 2 illustrates a left-side view of the prosthetic finger assembly ofFIG. 1;

FIG. 3 illustrates an exploded view of the prosthetic finger assembly ofFIGS. 1 and 2;

FIG. 4 illustrates a top view of the prosthetic finger assembly of FIGS.1-3, with a centerline axis bisecting the assembly relative to a y-axis;

FIG. 5 illustrates another left-side view of the prosthetic fingerassembly of FIGS. 1-4, with a midline axis intersecting first and secondhinged connections relative to a z-axis;

FIG. 6 illustrates an end view of the prosthetic finger assembly ofFIGS. 1-5, with an inserted shim;

FIG. 7 illustrates a flow chart depicting an exemplary method of fittingthe prosthetic finger assembly of FIGS. 1-6;

FIG. 8 illustrates a perspective view of one embodiment of a prostheticfinger device having a rocker connecting a tip with a distal linkage anda proximal linkage;

FIG. 9 illustrates a top view of the prosthetic finger device of FIG. 8;

FIG. 10 illustrates a right-side view of the prosthetic finger device ofFIGS. 8-9; and

FIG. 11 illustrates a left-side view of the prosthetic finger device ofFIGS. 8-10.

DETAILED DESCRIPTION

Embodiments are described more fully below in sufficient detail toenable those skilled in the art to practice the system and method.However, embodiments may be implemented in many different forms andshould not be construed as being limited to the embodiments set forthherein. The following detailed description is, therefore, not to betaken in a limiting sense.

Various embodiments disclosed herein relate to a custom-designed,self-contained prosthetic finger that can be fitted for a user with anamputated finger, fingertip, or finger segment. The streamlined,sophisticated, and biomechanically driven design allows for a patientwith any level of residual finger to utilize a mechanical replacementthat mimics the motions and functionalities of a real finger. Thenatural action of the prosthetic finger assembly allows users to regainmaximum control of the flexion and extension movements of a full fingerand fingertip and is designed to bend and curl in a realistic, naturalmanner in response to movement in the user's residual finger or adjacentfingers. The prosthetic finger described herein protects the amputationsite against further injury or hypersensitivity, while also providing anindividual with maximum fit and use flexibility, dexterity, gripstrength, and articulation. As a result, the prosthetic finger offersdigit amputees a functional solution that eases the transition back intodaily activities, no matter how intricate, after amputation.

FIGS. 1-3 illustrate perspective, side, and exploded views of oneembodiment of a prosthetic finger 100. In this embodiment, prostheticfinger 100 may include four major interconnected components that extendfrom a proximal end located at the patient's hand to a distal endlocated at a distance from the patient's hand. These components includea proximal ring 102, a distal ring 104, a coupling tip 106, and aY-shaped rocker 108. Proximal ring 102 and distal ring 104 may each havea respective body 112, 113. In this embodiment, bodies 112, 113 may formcircular or ring shapes that are configured to anchor onto apatient's/user's residual finger. More specifically, body 112 ofproximal ring 102 may be configured to anchor about a proximal phalanxof a user's residual finger with a snug fit. Similarly, body 113 ofdistal ring 104 may be configured to anchor about a middle phalanx of auser's residual finger with a snug fit.

A series of hinges may be used to secure the four primary componentsdiscussed above via rotative connections. In one embodiment, theserotative connections may be particularly positioned with respect to apair of axes detailed in FIGS. 4-5. More specifically, FIG. 4 depicts acenterline, C, that bisects prosthetic finger 100 relative to a y-axis,and FIG. 5 shows a midline, M, that intersects a first hinged connection110 and a second hinged connection 114, both detailed below, relative toa z-axis.

Turning to the various rotative connections shown in FIGS. 1-2, distalring 104 may rotatively couple with coupling tip 106 via first hingedconnection 110. First hinged connection 110 may include a pair ofparallel pivotal hinges that are symmetric about centerline, C,discussed above in relation to FIG. 4. Each of the pivotal hinges ofconnection 110 may provide a pivot point between distal ring 104 andcoupling tip 106.

Proximal ring 102 may rotatively couple with distal ring 104 via secondhinged connection 114. Second hinged connection 114 may also include apair of parallel pivotal hinges that are symmetric about the centerline,C, one located on each side of prosthetic finger 100 such that eachprovides a pivot point between proximal ring 102 and distal ring 104. Asdiscussed above in relation to FIG. 5, the midline, M, intersects hingedconnections 110 and 114, and, therefore, both first and second hingedconnections 110, 114 are located directly upon the midline, M, relativeto the z-axis.

As shown in FIG. 3, rocker 108 may form a Y-shape having opposing firstand second ends 116, 118, respectively, that extend between coupling tip106 and proximal ring 102. First end 116 may form a single prong of theY-shape and rotatively couple with coupling tip 106 via a third hingedconnection 120 (FIGS. 1-2) located below the midline, M, relative to thez-axis. Second end 118 may form a split prong of the Y-shape androtatively couple with proximal ring 102 via a fourth hinged connection122 (FIGS. 1-2) located above the midline, M, relative to the z-axis.Fourth hinged connection 122 may include a pair of parallel pivotalhinges that are symmetric about the centerline, C, each providing apivot point between rocker 108 and proximal ring 102.

Any one or more of the first, second, third, and/or fourth hingedconnections 110, 114, 120, 122 may be outfitted with hard-stops toprevent hyperextension of the finger during operation. For example, ahard-stop 127, shown in FIG. 1, may prevent relative over-rotation offirst hinged connection 110, or between distal ring 104 and coupling tip106. Mechanical hard-stops may have any appropriate size, shape, and/orconfiguration.

Working together, proximal ring 102, distal ring 104, coupling tip 106,and Y-shaped rocker 108 form a 4-bar linkage system that allows thecoupling tip to be articulated in response to a pulling force on distalring 104, which places the member in tension and reduces the risk ofbuckling. Thus, natural movement of the patient's residual finger seatedwithin proximal ring 102 and distal ring 104, or in some cases movementof his or her adjacent fingers, may be used to actuate realistic flexionand extension motions within prosthetic finger 100. Users may performtheir full range of usual activities, including typing, playing amusical instrument, or any other activity that requires the fulldexterity of the hand.

The Y-shape of rocker 108 is designed to reduce the overall bulk ofprosthetic finger 100. In this regard, third hinged connection 120occurs internally (i.e., within the physical boundary defined by distalring 104 and coupling tip 106) at the centerline, C. This configurationallows users with a relatively short residual finger, or a relativelyshort middle phalanx, to take advantage of a streamlined design thatdirects portions of rocker 108 inward. That said, while rocker 108 isdescribed herein as having a Y-shaped profile, it should be understoodthat rocker 108 may take any appropriate size, shape, type, and/orconfiguration desired to achieve maximum functionality.

In the embodiment shown in FIGS. 1-5, coupling tip 106 may include a tippad 124. Tip pad 124 may be formed from a soft-textured silicone orother material that mimics the texture of a real finger. This aids withgripping and provides a softer touch. In one embodiment, a touchscreenmechanism (not shown) may be provided to allow the user to use theprosthetic finger to operate capacitive touchscreens, which react to thebody's natural current. The touchscreen mechanism allows the user todirect his or her own body current through the tip of the prostheticfinger.

One embodiment of coupling tip 106 may also include a nail 126, whichmimics a natural edged nail that may provide scratching and peelingfunctionalities as well as assist with fine-object manipulation.

Embodiments of prosthetic finger 100 are custom designed andindividually fitted to accommodate a variety of differing userconditions, including different residual-finger lengths (e.g., varyingamounts of loss to the middle phalanx). In this regard, each finger 100may be customized to fit a particular patient or user, providing bothcustom functionality as well as a mechanical match to the anatomicaljoint articulation of the user, including matching the length of theoriginal, non-amputated finger. Design considerations include an amountof finger loss, a number of joints to be replaced, and othercharacteristics specific to the individual end user. In cases in whichthe user has a fully formed, but poorly or nonfunctioning finger,coupling tip 106 may be removed so that prosthetic finger 100 functionsas a joint brace, rather than a digit replacement. To further providebetter aesthetics, embodiments of finger 100 may be coated with filmsand/or colorings matched to the user's skin tone/color. An additivemanufacturing process (i.e., 3D printing) facilitates this ability tocustomize the intricacies of the prosthetic finger design in order tooptimize the device for each patient.

Embodiments of prosthetic finger 100 may be formed of any suitablestructural material that is non-irritating to human skin and allows theuser to operate the prosthetic with comfort and confidence. Exemplarymaterials include titanium, stainless steel, aluminum, silicone, carbonfiber, nylon, plastic/polymer, wood, rubber, gold, silver, tungsten,flex cable, neoprene, or any other suitable material. In one embodiment,components of prosthetic finger 100 are 3D printed from Duraform EXpolymer material. Using biocompatible materials, various embodiments offinger 100 may be applied as an orthopedic implant that may besurgically implanted into a user's finger. This option may be appliedfor users having injuries that have crushed their finger bones withoutthe ability to heal or be repaired. In these situations, implantableembodiments of prosthetic finger 100 are able to take the place of theuser's original bones without the need for amputation.

To use, the user may simply slide proximal ring 102 and distal ring 104onto his or her residual finger, and, if necessary, adjust further usinga shim(s). FIG. 6 depicts a rear view of prosthetic finger 100, in whichbody 112 of proximal ring 102 is outfitted with a semi-circular shim128, which may be employed to allow the sizing of body 112 to accountfor possible swelling in the fingers, weight gain, or any otherpost-manufacture changes in the size of the residual finger. In furtherdetail, a fit kit (not shown) may be provided with each prostheticfinger 100 and may include a number of shims 128. In one embodiment,each shim 128 may approximate a semi-circle or U-shape configured toabut an inner diameter, d, of body 112 of proximal ring 102 and may havea number of retaining grommets 130 configured to protrude throughcorresponding shim-retainment apertures 132 within body 112. Each shim128 may have a different thickness, t, thereby allowing the user toessentially adjust the inner diameter, d, of body 112 of proximal ring102 in a number of increments as required by the user.

Once prosthetic finger 100 (adjusted or otherwise) is in place, the usercan utilize his or her natural movements of the residual finger. Theprimary components of prosthetic finger 100 will articulate using thesame cognitive process that was previously utilized for the originalfinger. If a user wears multiple fingers 100, each may be individuallyoperated.

FIG. 7 provides a flow chart depicting an exemplary method 150 forinstalling and adjusting, or fitting, one embodiment of prostheticfinger 100 upon a user's residual finger. Method 150 details the fittingprocess with respect to proximal ring 102, but it should be understoodthat distal ring 104 may be fit or adjusted in a similar manner. Method150 begins with inserting (152) the residual finger into body 112 ofproximal ring 102 and assessing a tightness (154) of body 112 about theresidual finger. Depending on this assessment (154), the user, a medicalprofessional, or another assistant may select a first shim 128 (156)from the fit kit or another source. The user may then remove theresidual finger (158) from proximal ring 102 and insert first shim 128(160) into the inner diameter, d, of body 112 such that first shim 128lines the inner diameter, d, while retaining grommets 130 protrudethrough shim-retainment apertures 132. Once first shim is installed(160), the user may reinsert the residual finger (162) into proximalring 102 and assess a tightness (164) of first shim 128 (which now linesbody 112 of proximal ring 102) about the residual finger. If the shimmedproximal ring 102 fits, method 150 is complete (166), and the user mayproceed to biomechanically drive prosthetic finger 100. If shimmedproximal ring 102 does not fit, method 150 may return to the step ofselecting a shim (156), in which a second shim having a differentthickness may be selected before proceeding. The user may experimentwith multiple shims of varying thicknesses until an ideal or desired fitis achieved. Of course, distal ring 104 may be adjusted in a mannersimilar to that discussed with respect to proximal ring 102 and method150.

FIGS. 8-11 illustrate perspective, top, right-side, and left-side viewsof an alternate embodiment of a prosthetic finger 200. In thisembodiment, prosthetic finger 200 includes three primary interlinkedcomponents: a rocker 202 having a proximal end 204 and a distal end 206,a proximal linkage 208, and a distal linkage 210. In further detail, andas shown in FIGS. 8-9, distal linkage 210 may rotatively couple withproximal linkage 208, which may, in turn, couple with proximal end 204of rocker 202. Distal end 206 of rocker 202 may rotatively couple with atip 212 via a tip fastener joint 226, shown in FIGS. 8 and 11, thatallows tip 212 to be positioned at varying angles relative to theremainder of finger 200 in order to achieve different grip strengthsand/or articulation characteristics. A tip pad 214 may attach to tip212.

Two cage rings may attach to the linkages for the purpose of retaining auser's residual finger (with one ring proximal of the proximalinterphalangeal (“PIP”) joint and another ring distal of the PIP joint)and translating movement of the residual finger through the interlinkedassembly discussed above. As shown in FIGS. 8-11, a proximal cage ring216 and a distal cage ring 218 may attach to proximal linkage 208 anddistal linkage 210, respectively. This attachment may be facilitated bya universal ring mount 220 located on each of proximal linkage 208 anddistal linkage 210. Each universal ring mount 220 may define a ringmount aperture 224 that is configured to receive an attachmentprotrusion 222 of each of cage rings 216, 218. To use, a user/patientmay slide proximal and distal cage rings 216, 218 of prosthetic finger200 over his or her residual finger like a ring.

While prosthetic finger 200 may be custom designed to custom fit eachuser, post-manufacturing changes to the patient's physiology may occur.To add post-manufacturing customization capabilities to prostheticfinger 200, both proximal cage ring 216 and distal cage ring 218 may beinterchangeable such that they may be swapped out with rings of varyingsizes to address sizing and/or swelling issues demonstrated in theresidual finger of the patient. Varying sizes of proximal and distalcage rings 216, 218 may be provided in a fit kit (not shown), allowingthe user to employ the most appropriate ring sizes in real-time. Theuser may easily interchange cage rings by removing the rings 216, 218from, and replacing different rings to, ring mounts 220 via ring mountapertures 224 and attachment protrusions 222. Interchangeable rings 216,218 may be formed of any appropriate material including flexiblepolymers or other plastics that are non-irritating to human skin.

Embodiments of the prosthetic fingers 100, 200 described above exhibitnumerous unique characteristics and provide a variety of medicalbenefits. An individual's unique physiology and lifestyle patternsdictate the function and performance expected of his or her hands. Usingembodiments of the prosthetic fingers described herein, patients mayregain independent control of their hands, whether at work or at play.Each device is custom designed, manufactured for a specific individual,and incorporates features that allow for further fine-tuning andadjustment of fit to account for post-manufacturing fluctuations (e.g.,shims and or interchangeable rings), enabling the device to fit the userin a manner that allows for a biomechanically driven, low profile,lightweight, highly functioning return to the user's everydayactivities, no matter what those activities might entail. A few examplesinclude typing, playing the piano or another instrument, woodworking,and much more.

Embodiments of the prosthetic fingers described above are body powered,and their linked components articulate when the user simply moves his orher residual finger, when available, or an adjacent finger whennecessary. Beyond allowing for a simple, elegant, and streamlined designthat offers strength in the lowest possible profile design, employingthe user's own biomechanics to drive embodiments of prosthetic fingers100, 200 provides a host of medical benefits to the user, includingreduced swelling of and increased circulation to the residual finger andthe hand as a whole, supporting healthy joints in the injured andadjacent fingers.

Although the above embodiments have been described in language that isspecific to certain structures, elements, compositions, andmethodological steps, it is to be understood that the technology definedin the appended claims is not necessarily limited to the specificstructures, elements, compositions and/or steps described. Rather, thespecific aspects and steps are described as forms of implementing theclaimed technology. Since many embodiments of the technology can bepracticed without departing from the spirit and scope of the invention,the invention resides in the claims hereinafter appended.

1. A biomechanically driven prosthetic finger assembly, comprising: acoupling tip; a distal ring configured to anchor onto a residual finger,the distal ring rotatively coupled with the coupling tip via a firsthinged connection; a proximal ring configured to anchor onto theresidual finger, the proximal ring rotatively coupled with the distalring via a second hinged connection, wherein the first hinged connectionand the second hinged connection define a midline relative to a z-axis;and a rocker extending between the coupling tip and the proximal ring,the rocker having a first end and a second end in opposition to oneanother, the first end rotatively coupling with the coupling tip via athird hinged connection located below the midline, the second endrotatively coupling with the proximal ring via a fourth hingedconnection located above the midline; wherein the distal ring togetherwith the rocker are configured to utilize articulation movements of theresidual finger within the proximal and distal rings to emulate afinger's natural closing motion at the coupling tip.
 2. The prostheticfinger assembly of claim 1, wherein the rocker defines a Y-shape, thefirst end of the rocker forming a single prong of the Y-shape at thethird hinged connection, and the second end of the rocker forming asplit prong of the Y-shape at the fourth hinged connection.
 3. Theprosthetic finger assembly of claim 2, wherein a centerline bisects theprosthetic finger assembly relative to a y-axis, and wherein: the firsthinged connection comprises a pair of parallel pivotal hinges that aresymmetric about the centerline; the second hinged connection comprises apair of parallel pivotal hinges that are symmetric about the centerline;and the fourth hinged connection comprises a pair of parallel pivotalhinges that are symmetric about the centerline.
 4. The prosthetic fingerassembly of claim 1, wherein the distal ring is configured to anchorabout a middle phalanx of the residual finger with a snug fit, andwherein the proximal ring is configured to anchor about a proximalphalanx of the residual finger with a snug fit.
 5. The prosthetic fingerassembly of claim 1, wherein the coupling tip includes a grip-enhancingtip pad.
 6. The prosthetic finger assembly of claim 1, wherein at leastone of the proximal ring and the distal ring includes one or moreshim-retainment apertures configured to receive and retain a sizingshim.
 7. The prosthetic finger assembly of claim 1, wherein one or moreof the coupling tip, the distal ring, the proximal ring, and the rockerare 3D printed from an engineering-grade polymer.
 8. The prostheticfinger assembly of claim 1, further comprising one or more mechanicalhard-stops configured to prevent relative over-rotation at the first,second, third, or fourth hinged connections.
 9. A method of fitting acustomized prosthetic finger having a proximal ring configured to anchorto a patient's residual finger, the proximal ring containing one or moreshim-retainment apertures, comprising: inserting the residual fingerinto an interior of the proximal ring of the prosthetic finger;assessing a tightness of the proximal ring about the residual finger;selecting a first shim having a first thickness from a plurality ofshims configured to line the interior of the proximal ring, each of theshims including one or more retaining grommets; removing the prostheticfinger; inserting the first shim into the interior of the proximal ringsuch that the retaining grommets protrude through the shim-retainmentapertures, thereby retaining the first shim within the interior of theproximal ring; and reinserting the residual finger.
 10. The method ofclaim 9, further comprising: assessing a tightness of the first shimabout the residual finger; removing the prosthetic finger; removing thefirst shim; selecting, from the plurality of shims, a second shim havinga second thickness; and inserting the second shim into the interior ofthe proximal ring such that the retaining grommets protrude through theshim-retainment apertures, thereby retaining the second shim within theinterior of the proximal ring.
 11. The method of claim 9, wherein eachof the plurality of shims has a different thickness.
 12. The method ofclaim 9, wherein the shims are formed of polymer.
 13. The method ofclaim 9, wherein each of the shims has a shape that approximates asemi-circle.
 14. A prosthetic finger device, comprising: a rocker havinga proximal end and a distal end; a tip operably connected with thedistal end of the rocker; a distal linkage operably connected with aproximal linkage, the proximal linkage in operable connection with theproximal end of the rocker; a first proximal cage ring coupled with theproximal linkage; and a first distal cage ring coupled with the distallinkage. 15-20. (canceled)